Our Skin Is Covered With Invisible Stripes

Envy the tiger and the zebra no longer. You have stripes of your own.

Human skin is overlaid with what dermatologists call Blaschko’s Lines, a pattern of stripes covering the body from head to toe. The stripes run up and down your arms and legs and hug your torso. They wrap around the back of your head like a speed skater’s aerodynamic hood and across your face. Or they would, if you could see them.

In the early 1900s, German dermatologist Alfred Blaschko reported that many of his patients’ rashes and moles seemed to follow similar formations, almost as though they were tracing invisible lines. But those lines didn’t follow nerves or blood vessels. They didn’t represent any known body system.

Here is how Blaschko depicted these lines in an early paper:

Wikimedia Commons // Public Domain

It turns out these lines are far more extensive than even Blaschko thought—closer to this:

Davide Brunelli, Med Art


And today we know what they are: cellular relics of our development from a single cell to a fully formed human. Each one of us started out as a single cell, and then a little glob of cells. As the cells divided, they differentiated. Some became muscles, others bones, still others organs. And some became skin. As those skin cells continued dividing, they expanded and stretched to cover a quickly growing body. One cell line pushed and swirled through another like steamed milk poured into an espresso to make a latte.

Blaschko’s lines are the molecular evidence of those swirls.

Most people will never see their own stripes. As Dr. Blaschko noted, there are dozens of skin conditions that follow these lines, but most of them affect patches of skin or a single body part, not the entire body. Lined and whorled nevoid hypermelanosis can create beautiful patterns.

And then there are the chimeras. Remember the single cell that turned into a glob? From time to time, two of these starter cells will merge and become a glob together. The glob eventually resolves into a chimera: an animal with two lines of DNA. As the animal’s skin develops, the two groups of cells divide and swirl just like non-chimera skin cells. The difference is that the two groups of chimerical cells are slightly different from each other. Behold the chimera cat Venus:

Sometimes, this difference is obvious. More often in humans, though, it’s too subtle to notice with the naked eye, and can only be spotted under UV light.

Amazon's Under-the-Radar Coupon Page Features Deals on Home Goods, Electronics, and Groceries

Stock Catalog, Flickr // CC BY 2.0
Stock Catalog, Flickr // CC BY 2.0

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Now that Prime Day is over, and with Black Friday and Cyber Monday still a few weeks away, online deals may seem harder to come by. And while it can be a hassle to scour the internet for promo codes, buy-one-get-one deals, and flash sales, Amazon actually has an extensive coupon page you might not know about that features deals to look through every day.

As pointed out by People, the coupon page breaks deals down by categories, like electronics, home & kitchen, and groceries (the coupons even work with SNAP benefits). Since most of the deals revolve around the essentials, it's easy to stock up on items like Cottonelle toilet paper, Tide Pods, Cascade dishwasher detergent, and a 50 pack of surgical masks whenever you're running low.

But the low prices don't just stop at necessities. If you’re looking for the best deal on headphones, all you have to do is go to the electronics coupon page and it will bring up a deal on these COWIN E7 PRO noise-canceling headphones, which are now $80, thanks to a $10 coupon you could have missed.

Alternatively, if you are looking for deals on specific brands, you can search for their coupons from the page. So if you've had your eye on the Homall S-Racer gaming chair, you’ll find there's currently a coupon that saves you 5 percent, thanks to a simple search.

To discover all the deals you have been missing out on, head over to the Amazon Coupons page.

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30 Pungent Facts About Farts

This man is clearly not trying to hide the fact he just passed gas.
This man is clearly not trying to hide the fact he just passed gas.
BrilliantEye/iStock via Getty Images

Whether you openly admit it or desperately try to hide it, it’s an undeniable fact that every living and breathing human being farts. And while passing what you thought was going to be silent gas only to be wrong in certain situations can definitely be embarrassing, there’s something undeniably humorous about flatulence—no matter your age.

If you do love a good fart joke, you’re in good company. The very first recorded joke, which was written by the Sumerians and dates all the way back to 1900 BCE, was about—you guessed it—breaking wind. And some of the world's great thinkers, from William Shakespeare to J.D. Salinger, have slipped a fart joke (or 10) into their work.

In this episode of The List Show, we're sniffing out 30 fascinating facts about farts—from why humans expel gas to how often the average adult squeezes the cheese. You can watch the full episode below.

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